This application will focus on characterizing essential genes in Streptococcus mutans involved in plaque formation and growth. Utilizing model in vitro systems, genes essential for biofilm formation will be identified and characterized following insertion duplication mutagenisis of S. mutans GS5. In addition, two genes recently identified in our laboratory as important for this process, comB and sgp, will be further analyzed as to their respective roles in biofilm formation. Potential signal transduction mechanisms involving both genes will be investigated using gene expression techniques in addition, the role of the com system in inraspecies quorum sensing relative to gene transfer and biofilm formation will be assessed. A novel approach developed in this laboratory to identify essential genes in any transformable microorganism will be utilized to identify such genes in S. mutans this approach, based upon antisense RNA induction, has the potential of identifying target sites for the development of specificanticaries agents. In addition, this approach can be readily used to identify essential genes in ubiquitous bacteria for development of broad- spectrum antibacterial agents. The specific aims of this proposal are designed to provide new information regarding essential virulence factors of S. mutans which could be exploited to design novel anticaries strategies.